1. Field of the Invention
The present invention relates to telecommunication technology and, more particularly, the invention is directed to optimization of the route of a telecommunication connection that is set up in a mobile communication network.
2. Description of Related Art
For a teleoperator, i.e. an owner or operator of a telecommunications network, it is important that telecommunication connections be set up in an optimal manner. Optimization may for example be based on the length of the route of the connection or on the network load resulting from the connection. Because the traffic in mobile communication networks is continuously increasing, it is particularly important that the load in such networks remain as low as possible. One approach to reducing the load in a mobile communication network is to set up or establish the connection to the mobile switching center then serving the called subscriber via a route that is as short as possible.
An intelligent network is formed by switching, control and functional components and a signaling network. A service switching point (SSP) of such intelligent networks is a modified telephone exchange that analyzes the traffic passing therethrough. When the SSP detects a certain number that meets a triggering criterion, it transmits a service request to a service control point (SCP). The information required for service control is stored in a service data point (SDP), from which the service control point can obtain the information that it needs.
Service switching points are connected via signaling channels to service control points, which implement intelligent network services by utilizing a service database. A service control point may for example perform a numerical conversion from the B-number to the corresponding C-number by accessing such correspondence information from the service database.
The communication protocols used in an intelligent network are rules by which the components of the intelligent network talk to each other. These protocols defme the interfaces between components as well as the structure of the messages exchanged between them. Intelligent network components communicate with each other using common channel signaling (CCS). By ITU-T definition, common channel signaling is known as CCSS No 7. For communication between components, an intelligent network uses the services of the INAP (Intelligent Network Application Part) defined by ITU-T; the INAP application part is an intelligent network application protocol used, for example, for communication between a service control point and a service switching point. The MAP application part, on the other hand, is a portion of the signaling system of a mobile communication network that is used for signaling between the switching centers and registers of the mobile communication network.
In the GSM (Global System for Mobile communications) system, a call to be set up or established is routed as follows. A call setup request is sent from the calling subscriber""s (A-subscriber""s) terminal equipment to a gateway mobile switching center (GMSC), which then sends a query to the called subscriber""s (B-subscriber""s) home location register (HLR) to determine the mobile switching center (MSC) under which the B-subscriber""s terminal device is currently located. The home location register is implemented as a database that contains such information as subscriber data, subscriber location data, call control data, short-message services and billing data.
Next, the home location register requests the visitor location register (VLR) for a roaming number MSRN (Mobile Subscriber Roaming Number) and returns the roaming number to the GMSC. The visitor location register is implemented as a database in a mobile communication network which contains the information required for the transmission of calls about each mobile subscriber currently located in the area of the network. The roaming number is a temporary identification number that is allocated to a mobile station recorded in the visitor location register and which is used by the mobile communication system for the routing of calls addressed to that particular subscriber.
Based on the roaming number, the GMSC then routes the call originated by the A-subscriber to the mobile switching center in whose location area (LA) the B-subscriber is currently located. The B-subscriber""s mobile switching center in turn sets up a connection with the B-subscriber""s terminal device.
The primary problem with the above-described routing procedure is that calls addressed to mobile stations are not automatically routed via the shortest route to the proper mobile switching center but may, instead, be routed via several switching centers. One solution that has been applied to eliminate this problem is to provide some service nodes (SN) and service control points with an MAP interface, thus making it possible to implement functionality and service similar to that provided by present invention. Such solutions, however, disadvantageously they bind the service to a certain base and assume that the service control point or service node is provided with an MAP interface.
In the procedure of the present invention, on the other hand, the routing of calls addressed to a terminal device is optimized by using an intelligent network service and a special gateway. By means of that gateway, a query is sent from the intelligent network system to a subscriber register to obtain B-subscriber data and, using that data, the call to be set up is routed directly to the mobile switching center in whose area the B-subscriber""s terminal device is currently located. This arrangement and methodology additionally makes it possible to utilize other GSM network services.
It is accordingly the desideratum of the present invention to eliminate, or at least significantly reduce, the drawbacks and deficiencies of the prior art, as for example described hereinabove.
It is a particular object of the invention is to provide a new type of procedure and system for routing a new call being set up directly to the mobile switching center under which the B-subscriber is currently located.
The procedure of the invention is thus utilized to optimize the route of a telecommunication connection to be set up, as for example and preferably in a mobile communication system.
The telecommunication system of the present invention comprises a mobile switching center, a service switching point, a service control point, a gateway, and a subscriber register. The service switching point is connected to the service control point, and the subscriber register and service control point are connected to the gateway. The gateway further comprises means for handling a database query, a signaling query, a response to a database query, and a response to a signaling query.
In the method of the present invention, a telecommunication connection to be set up is directed via the service switching point to the service control point. From the service control point, a database query is performed, which is directed to the gateway. The database query is converted in the gateway into a signaling query which is sent to the subscriber register. Using the data in the subscriber register, a response to the signaling query is defined and returned to the gateway, at which the response to the signaling query is converted to a response to the database query, on the basis of which the service control point determines an optimal route to the appropriate mobile switching center.
In preferred embodiments of the invention, the response to the signaling query contains routing information which is used to optimize the route of the telecommunication connection to the mobile switching center. A connection to the mobile switching center, and further by way of example to the B-subscriber""s terminal device, is then set up. The routing information may for example be a roaming number, such preferably as the Mobile Subscriber to Roaming Number MSRN.
In the same or other preferred embodiments of the invention, the gateway may be an MAP-INAP gateway, which comprises means for controlling the interface between the service control point and the database and means for controlling the interface between the gateway mobile services switching center and the subscriber register. The signaling query is preferably an MAP (Mobile Application Part) query and the database query an SDP (Service Data Point) query. As a consequence of this arrangement, the service control point of the intelligent network is able to use the subscriber data of the GSM network.
In these or other preferred embodiments of the invention, the subscriber register may be the home location register of the GSM system.
The present invention thus allows optimal routing to the mobile switching center under which the B-subscriber is then or currently located. If, according to the data in the visitor location register, the subscriber cannot be reached, then corresponding information is obtained. If the subscriber has transferred his or her calls to another number using the CFU (Call Forwarding Unconditional) supplementary service, this too will be known so that the call can be properly routed to the specified forward number.
As will be further appreciated, the inventive solution advantageously does not require any changes in the elements of the mobile communication network or in the intelligent network because the invention implements the enhanced service through the use of a separate MAP-INAP base.